Without further info it is difficult to advise but my guess is that you have what is called an
Intermediate Switch with 4 connections like this one.
Edited: Image links not working!
OR - It may just be a 2 way switch with 3 connections like this one -
Edited: Image links not working!
A photo or two of the back of the existing switch and a description of what is does - I.E. what it operates would be handy.
If it IS an intermediate switch, then you should be able to get one from where you got the other new switches.
Over to you
TT